The invention relates to a system for generating electric energy from fuels having electrochemically acting fuel cells with arrangements for the feeding and removing of the reacting substances and of the reaction products to and from reaction spaces on the surfaces of the electrodes of the fuel cells. A heat exchanger is provided for regulating the heat and for processing the substance flows into and out of the fuel cells.
Such a type of system is known from the encyclopedia "Naturwissenschaft und Technik" ("Natural Science and Technology"), Zweiburgen-Verlag Weinheim, Volume 1, 1979, Pages 585-593, as the current state of the art. Here a fuel cell is formed by two electrodes serving as the catalyst which are separated from one another by means of an electrolyte. Conventional fossil fuels are used as fuel for the fuel cell. A mixture of water vapor, fuel vapors and a catalyst gas is supplied at the fuel electrode which results in the generating of carbon dioxide, hydrogen ions and electrons. The hydrogen ions travel through an electrolyte to the air electrode, at which location combustion air is supplied and where water vapor is generated in a hydrogen ion/oxygen reaction. In order to achieve higher electric outputs, stacks of fuel cells are formed which are connected in series. For the operation of such fuel cells, devices are naturally required for feeding and removing the reactive substances and the reaction products to and from the spaces bordering on the electrode surfaces as well as devices for controlling the heat, e.g. heat exchangers. The systems which are currently operative have not exceeded individual limited special applications because of low efficiency. The reason is that no consequent reprocessing and reuse of the substances participating in the process and utilization of occurring heat quantities has taken place.
The invention is based on the object of providing a system for generating electric energy which is based on the use of fuel cells, which have a high efficiency and which can be operated in an economical and environmentally advantageous manner.
In the case of a system of this type, this object is achieved by a heat exchanger assigned to the fuel cell which is used for the cooling of the substance flows carried away from the fuel cell and for the precipitation of the condensates contained therein. The heat exchanger uses the resulting obtained heat for heating and evaporating of the substance flows to be supplied to the fuel cell. A gas washing unit is used for the separation of catalyst gas used in the fuel cell and residual fuel components from fuel gases removed from the fuel cell. These separated elements are fed back into the fuel cells. By means of suitable heat exchangers and arrangements, heat quantities occurring in the process are reutilized for the heating of the substance flows to be fed to the fuel cell. Other system parts have the purposes of: purifying the fuel gases occurring during the fuel reaction by means of gas washing units, and of returning the residual fuel components to the fuel cells and of recovering expensive catalyst gases.
It is advantageous if a second gas washing unit is provided in which the carbon dioxide contained in the fuel gases is dissolved and removed in a transport fluid, and wherein a residual gas mixture is precipitated out and through suitable arrangements is also fed back into the fuel cell. The precipitation apparatus provides for the reprocessing of the transport fluid with the emission of carbon dioxide to the ambient air. The transport fluid is guided in a closed loop between the gas washing unit and the precipitating apparatus. A heat exchanger is provided for the heat exchange between the fluid flows. Also, regenerating apparatus is provided for regenerating the residual catalyst gas and for separating poisonous gases from the transport fluid.
It is further advantageous to have a heat pump which is used for the cooling of the gas washing units by way of the heat exchangers and which makes available the regenerated heat for the heating of a vapor generator and the precipitating apparatus for the reprocessing of the transport fluid. Combustion air flow is controlled by valves in the supply and discharge line to the fuel cell. The flow of the fuel gas mixture to the fuel cell is controlled by a valve in the discharge line leading to the gas washing unit and by controlling the generating of vapor by means of a vapor generator in the supply line. here fuel injection is controlled by means of an arrangement for measuring the cell voltage.
It is also desirable to have the fuel cells arranged in stacks wherein at least the gas mixture containing the fuel is guided successively through the individual fuel cells of the stack in a serpentine course. The supplying of water to the fuel-gas-mixture-side electrode of the fuel cell is controlled as a function of its concentration in the fuel condensate which is precipitated in the heat exchanger. Microprocessor controlled pumps and valves are provided for the feeding and removal of the substance flows to and from the fuel cell.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings